Burner Assembly

ABSTRACT

A burner assembly comprising a burner element ( 8 ) at which gas is combusted. A valve ( 2 ) allows selective release of gas from a source into an expandable space ( 4 ) when the valve is opened. The space is expanadable up to a fixed volume ( 3 ) against the action of a restoring means. The space is arranged to contract under the action of the restoring means to force gas out of the space and to the burner element.

The present invention relates to a burner assembly.

In our earlier application, PCT/GB2005/002735, we disclosed a heater forheating an active agent selected from cleaning, personal care,pesticidal and air care agents. The heater uses a gas burner in order toprovide the heat.

Such a heater is particularly advantageous in that as it has an on-boardpower source, it offers the convenience and portability of abattery-based system. However, it is able to generate much higher levelsof heat in a much shorter space of time than a battery-based system.

The present invention is directed to an improvement of such a heatingsystem.

According to the present invention, there is provided a burner assembly,comprising a burner element at which gas is combusted, a gas source, avalve to allow selective release of gas from the source, an expandablespace to which gas from the gas source is arranged to flow when thevalve is opened, the space being expandable up to a fixed volume againstthe action of a restoring means, the space being arranged to contractunder the action of the restoring means to force gas out of the spaceand to the burner element.

The expandable space and restoring means effectively act as aflow-smoothing device. In practice, gas leaving the gas source is not aconsistent gas phase. The balloon smoothes this flow providing aconstant flow to the burner thereby providing efficient and reliablecombustion.

The expandable space may be provided, for example, by a piston in acylinder. In this case, the restoring means may be a resilient membersuch as a spring against which the piston moves, or may be a closed gasvolume, the pressure of which increases as the expandable space isfilled with gas and decreases as the gas is expelled.

However, preferably, the expandable space'is provided by a resilientmember such as a balloon housed within a rigid container which definesthe fixed volume. Such an arrangement has the advantage that it can beimplemented at low cost. The rigid container may be sealed and may bepressurised prior to balloon expansion to exert greater force on theballoon. Alternatively, it may have one or more small holes to provideless of a force on the balloon.

The valve may be an integral part of the gas source. In this case, anactuator is provided to depress the valve. The actuator may either movethe valve element itself or may be configured to move the gas sourceitself while the valve is restrained thereby, effectively depressing thevalve with respect to the gas source.

However, preferably, the valve is separate from the gas source. Thevalve preferably comprises a manually operable member which the userpresses to initiate the release of gas. The valve is preferably a timedvalve which is configured to close automatically at a pre-determinedtime after it is opened.

The burner may have an ignition system which is activated independentlyof the valve. However, preferably, the burner assembly has an ignitionsystem which is activated by the manually operable member. As a safetyfeature, the manually operable member is preferably configured to stopthe gas flow from the gas source prior to initiating ignition.

The burner may be any suitable burner, but is preferably a catalyticburner. In order to provide an even distribution of heat from thecatalytic burner, a heat distribution plate is preferably provideddownstream of and spaced from the catalytic burner. The plate ispreferably provided with a plurality of holes to promote air flowthrough the plate and hence, enhance the heat distribution. Preferably,the holes furthest from the burner are larger than those closer to theburner as this encourages preferential air flow towards the periphery ofthe plate thereby ensuring even heat distribution.

An example of a burner in accordance with the present invention will nowbe described with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram of the burner assembly; and

FIG. 2 is a schematic diagram of the same assembly in a secondconfiguration.

The burner can be used to heat any active agent selected from thecleaning, personal care, pesticidal and air care agents. The full rangeof such agents is set out in PCT/032005/002735 and will not be repeatedhere as this invention is concerned with an improvement in the burnersystem, per se. However, the described burner of the particular examplehas been designed to heat wax strips which are useful in removing bodyhair.

The burner assembly comprises a source of combustible gas. In this case,a butane gas canister 1. Flow through the-gas canister is controlled bya valve 2. This is a timed valve which is designed to remain open for afixed period following actuation as described in more detail below.Downstream of the valve 2 is a rigid chamber 3 in which an expandableballoon 4 is mounted. The expandable balloon receives gas from thecanister 1 along inlet line 5 and expels gas along outlet line 6 asdescribed below. The outlet line 6 leads via a flow restriction 7 to acatalytic burner 8 which is well-known in the art.

A piezo-electric ignition electrode 9 is positioned in close proximityto the burner 8 so that a spark is generated between the electrode 9 andburner 8 to ignite the gas. A metal flow distribution plate 10 isprovided above and spaced from the burner 8. This plate has a pluralityof holes 11 which are larger away from the burner 8 to ensure an evendistribution of heat across the plate.

In use, a user will place, a wax strip on the plate 10 and will thenoperate the valve 2. This is done by depressing a manually depressiblemember (not shown) against the action of a spring. The manuallydepressible member has a helical groove which co-operates with acomplimentary follower to cause it to rotate as it is depressed, therotation opening the valve 2 to allow gas to flow from the burner 1 intothe balloon 4 thereby expanding the balloon as shown in FIG. 2. Furtherrotation of the valve 2 causes the follower to pass beyond the end ofthe helical groove. At this time, the user feels a click so that theyinstinctively know how to release the button. This releases the manuallyoperable member and the spring, then urges it back to its startingposition. On its return stroke, the manually operable member closes thevalve 2. The manually operable member has a lug which operates apiezo-electric spark generator in order to generate a spark at electrode9 to ignite the gas. This is timed to be generated after the valve 2 hasshut off the flow of gas from the gas canister 1. Typically, the timefor which the valve 2 is open will be-very short (approximately 1 to 10seconds) as a short burst of gas is all that is required to fill theballoon 4. Once full, the pressure generated by the resilience of theballoon 4 is sufficient to force the gas out of the balloon. Thepressures in the system ensure that this gas is forced out of outletline 6 rather than the inlet line 5. The gas 6 flows through the flowrestriction 7 to the burner 8 where it is ignited by the spark togenerate heat. Typically, the rigid chamber 3 and balloon 4 have avolume of 1 to 40 cm³ and are designed to provide a flow of gas to theburner for around 1 to 60 seconds. In one particular, example, thebutton is pressed filling the balloon in 0.5 seconds, 0.1 seconds laterthe valve is closed, and 0.1 seconds after that the ignition produces aspark. The gas finishes burning 16 seconds after the button is pressed.

In alternative embodiments, the balloon 4 may be replaced by a pistonwhich, as it is displaced to the right as shown in FIG. 1, bears againsta spring or compresses gas to generate a restoring force on the piston.

As an alternative to the valve 2, an actuation mechanism may be used todepress a valve in the canister 1 either by directly pressing the valvestem, or by moving the canister 1 against a fixed stop which contactsthe valve stem and causes it to be depressed into the canister 1 uponfurther movement of the canister 1.

1. A burner assembly comprising a burner element at which gas iscombusted, a gas source, a valve to allow selective release of gas fromthe source, an expandable space to which gas from the gas source isarranged to flow when the valve is opened, the space being expandable upto a fixed volume against the action of a restoring means, the spacebeing arranged to contract under the action of the restoring means toforce gas out of the space and to the burner element.
 2. An assemblyaccording to claim 1, wherein the restoring means is a resilient member.3. An assembly according to claim 2, wherein the resilient member is aballoon.
 4. An assembly according to claim 1, wherein the valve isseparate from the gas source.
 5. An assembly according to claim 4,wherein the valve comprises a manually operable member which the userpresses to initiate the release of gas.
 6. An assembly according toclaim 4, wherein the valve is a timed valve which is configured to closeautomatically at a predetermined time after it is opened.
 7. An assemblyaccording to claim 1, further comprising an ignition system which isactivated by the manually operable member.
 8. An assembly according toclaim 1, wherein the burner is a catalytic burner.
 9. An assemblyaccording to claim 1, further comprising a heat distribution plateprovided downstream of and spaced from the burner.
 10. An assemblyaccording to claim 9, wherein the plate is provided with a plurality ofholes to promote air flow through the plate.
 11. An assembly accordingto claim 10, wherein the holes furthest from the burner are larger thanthose closer to the burner.